This invention relates to visual displays in programmable electronic space thermostats which control operation of a heating and/or cooling system according to a programmed time-temperature schedule.
Thermostats having the capability of automatically switching from one level of temperature to be maintained in a space to another level at specific times, such thermostats sometimes referred to as set-back thermostats, generally require the user to perform some degree of programming or adjusting to establish a desired time-temperature schedule of operation. Once a set-back thermostat has been so programmed or adjusted, the user may easily forget the specific times and temperatures involved in the schedule, and thereafter simply rely on the visual display on the thermostat for such information.
In thermostats that are primarily electromechanical, the scheduled values of temperature, sometimes referred to as the setpoints, are generally set by a lever or knob which cooperates with an appropriate indicia of temperature values so as to enable the user to readily see, at a glance, the scheduled values of temperature. The scheduled values of times at which the levels of temperature are to be changed is also generally readily visible. For example, such thermostats often include a timer having a clock face with a plurality of tabs or pins attached to the outer perimeter thereof. Each such tab or pin, which includes a portion to mechanically effect the change in the level of temperature by operating a switch, for example, also includes a portion which cooperates with indicia on the clock face to visibly indicate the clock time at which such change occurs.
In thermostats that are primarily electronic, the time-temperature schedule is generally programmed by means of a key pad or slide switches. When slide switches are used, the scheduled times and temperatures are readily visible by simply looking at the slide switches and their cooperating indicia. When a key pad is used, the present scheduled temperature (setpoint) is generally continuously displayed in an electro-optical display, along with the present time and present sensed temperature. However, neither the values of the other scheduled temperatures nor the values of the scheduled times are continuously displayed. If the user wants to know, for any reason, what the programmed time-temperature schedule is, he must know what procedure to use to obtain this information and then must execute such procedure. Typically, at least one key must be depressed one or more times to effect a visible indication of the time-temperature schedule on a display. While such manipulation of a key or key pad is not necessarily difficult, it is inconvenient and it raises the possibility of accidentally touching the wrong key or operating a single key improperly, and thereby inadvertently changing other parameters of the time-temperature schedule.
When there are only two scheduled temperatures involved, it is believed unnecessary to continuously display both scheduled temperatures at the same time. That is to say, when only two temperatures values are involved, one of which is chosen to provide a level of comfort and the other to provide an energy savings, it is believed that these values, once chosen by the user, would thereafter generally be acceptable to the user and not be constantly adjusted. However, it is believed desirable that the time schedule be continuously displayed. For example, if the user unexpectedly spends a day at home or has late company, he may want to know exactly when the comfort level of temperature is programmed to prevail. When the time schedule is continuously displayed, the user can thus see the time schedule, at a glance, without any manipulation of any portion of the thermostat.